This invention is generally directed to a novel controller which is used in an air braking system for a vehicle, such as a semi-trailer or the like, which rids the braking system of any accumulated moisture or liquid therein thereby preventing possible problems in the braking of the vehicle. More particularly, the invention contemplates a braking system which includes a one-way pressure relief valve which is used to rid the braking system of moisture and liquid therein.
Braking systems in semi-trailers commonly include a controller which is in fluid communication with the brakes of the trailer, an air source for supplying air to the brakes of the trailer and an air signal that is supplied from the front of the trailer by the application of the trailer's brakes. The controller includes a piston member which is housed within a housing. The piston member separates the housing into a top chamber and a bottom chamber. The piston member moves relative to the housing to move a spool valve which is associated therewith to selectively allow the air from the source to be supplied to the brakes when a preset air pressure acts against the piston member from the air signal to cause the piston member to move within the housing.
A choke hole is provided at the interconnection of where the air signal is applied to the controller through a signal air inlet port and the top chamber of the housing. The choke hole is used to prevent piston flutter when rapid application, i.e. high pressure, of the air signal is present.
The piston member has a sump therein. When the piston sump fills with liquid, the piston member, in combination with the choke port, acts as a hydraulic dampener which makes the spool valve apply and release very slowly. This is a fairly common problem in the winter due to alcohol being added in the brake line at the front of the trailer air coupling in an attempt to prevent the piston member from freezing.
The alcohol reacts with the plastic material from which the piston member is made and causes the plastic piston member to expand. This deters the brake from releasing which can cause the brakes to lock up and burn.
Even without adding alcohol to the braking system, the braking system sometimes locks up and burns. During summertime operation of the braking system, moisture condenses in the brake lines and is fed by gravity down to the controller which is usually located approximately three to four feet lower than the air connection at the front of the semi-trailer. Over time, as the air signal which has moisture therein is applied and released, moisture accumulates and becomes trapped in the piston sump.
Thus, there is need for an improvement to current braking systems to rid the system of liquid and moisture. The present invention is intended to present such an improvement as well as to present several other advantages which are not found in the prior art.